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FreeBSD-SA-04:06.ipv6                                       Security Advisory
                                                          The FreeBSD Project

Topic:          setsockopt(2) IPv6 sockets input validation error

Category:       core
Module:         kernel
Announced:      2004-03-29
Credits:        Katsuhisa ABE, Colin Percival
Affects:        FreeBSD 5.2-RELEASE
Corrected:      2004-03-29 14:01:33 UTC (RELENG_5_2, 5.2.1-RELEASE-p4)
CVE Name:       CAN-2004-0370
FreeBSD only:   YES

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
<URL:http://www.freebsd.org/security/>.

I.   Background

IPv6 is a new Internet Protocol, designed to replace (and avoid many of
the problems with) the current Internet Protocol (version 4).  FreeBSD
uses the KAME Project IPv6 implementation.

Applications may manipulate the behavior of an IPv6 socket using the
setsockopt(2) system call.

II.  Problem Description

A programming error in the handling of some IPv6 socket options within
the setsockopt(2) system call may result in memory locations being
accessed without proper validation.  While the problem originates in
code from the KAME Project, it does not affect other operating systems.

III. Impact

It may be possible for a local attacker to read portions of kernel
memory, resulting in disclosure of sensitive information.  A local
attacker can cause a system panic.

IV.  Workaround

Do one of the following:

1) Disable IPv6 entirely by following these steps:

   - Remove or comment out any lines mentioning `INET6' from your
     kernel configuration file, and recompile your kernel as described
     in <URL:http://www.freebsd.org/handbook/kernelconfig.html>.

   - Reboot your system.

2) If all untrusted users are confined within a jail(8), ensure that
the security.jail.socket_unixiproute_only sysctl is set to 1 and
verify that no IPv6 sockets are currently open:

# sysctl security.jail.socket_unixiproute_only=1
# sockstat -6

This will restrict jailed processes to creating UNIX domain, IPv4, and
routing sockets, which are not vulnerable to this problem; note however
that processes inside a jail may still be able to inherit IPv6 sockets
from outside the jail, so this may not be sufficient for all systems.

V.   Solution

Do one of the following:

1) Upgrade your vulnerable system to the RELENG_5_2 security branch
dated after the correction date.

2) To patch your present system:

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:06/ipv6.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:06/ipv6.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the kernel as described in
<URL:http://www.freebsd.org/handbook/kernelconfig.html> and reboot the
system.

d) Install updated kernel headers.

# cd /usr/src/include
# make install

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

Branch                                                           Revision
  Path
- -------------------------------------------------------------------------
RELENG_5_2
  src/UPDATING                                                 1.282.2.12
  src/sys/netinet6/ip6_output.c                                  1.71.2.2
  src/sys/netinet/ip6.h                                          1.10.2.1
  src/sys/conf/newvers.sh                                       1.56.2.11
- -------------------------------------------------------------------------
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